This invention relates generally to the cleaning of semiconductor elements and, more particularly to a programmable method and apparatus for cleaning the surface of wafers, pre-cleaning circuit boards for assembly, removing flux from assembled circuit boards, and cleaning failed circuit boards prior to and during repair.
Cleaning of semiconductor surfaces is often necessary in the manufacturing of semiconductor products such as wafers, circuit boards, and the like. Cleaning may be required at various stages of processing, such as preparing surfaces for later processing, removing materials such as flux or photoresist, removing debris and contaminants, or cleaning surfaces before rework or repair. Proper cleaning of surfaces in the manufacturing process is important since inadequately cleaned surfaces can lead to quality problems of in-process failures, low yields, or reduced operating performance.
U.S. Pat. No. 3,489,608 issued Jan. 13, 1970 to Jacobs et al. for "Method and Apparatus for Treating Semiconductor Wafers" discloses the cleaning of wafers upon a rotating turntable within a chamber. Each wafer is held on a pedestal by a vacuum chuck around the periphery of the table surface. Liquid is dispensed onto the wafers from above while the turntable rotates about an axis perpendicular to the table center. After cleaning, gas is provided to dry the wafers.
U.S. Pat. No. 4,027,686 issued Jun. 7, 1977 to Shortes et al. for "Method and Apparatus for Cleaning the Surface of a Semiconductor Slice with a Liquid Spray of De-ionized Water" discloses a cleaning apparatus in which a wafer is held on a pedestal in a cleaning chamber with three nozzles directed at angles to the wafer surface. The pedestal has a vacuum chuck for holding the wafer in position, and the pedestal is turned to rotate the wafer. During rotation of the wafer around an axis perpendicular to its supporting pedestal, the first nozzle delivers high pressure de-ionized water, and then a second nozzle delivers lower pressure de-ionized water. After cleaning, gas is provided through the third nozzle for drying.
U.S. Pat. No. 4,112,454 issued Sep. 5, 1978 to Harvey et al. for "Method and Apparatus for Treating Elements of Photographic Film" discloses the immersion in a solution of a spindle holding film discs which are stacked in parallel layers upon the periphery of the spindle. The spindle is rotated around an axis through the center of the spindle to provide motion between the discs and the solution. A motor above the immersion chamber is attached to the spindle to provide rotational motion.
U.S. Pat. No. 4,197,000 issued Apr. 8, 1980 to Blackwood for "Positive Developing Method and Apparatus" discloses a stack of semiconductor wafers within a chamber which is rotated upon an axis through the center of the stack. Sprayers along the side walls of the chamber direct a liquid upon the rotating stack to remove photoresist from the wafers. The same sprayers are also used to rinse the wafers with de-ionized water, and then to provide a heated drying gas.
U.S. Pat. No. 4,489,740 issued Dec. 25, 1984 to Rattan et al. for "Disc Cleaning Machine" discloses an apparatus for rotating an annular disk around a central vertical axis while upper and lower nozzles dispense fluid as the nozzles sweep across the disc. Further, extensible arms may be provided from the center spindle which operate by centrifugal force to hold the disc in place during spindle rotation.
U.S. Pat. No. 4,519,846 issued May 28, 1985 to Aigo for "Process for Washing and Drying a Semiconductor Element" discloses a process for holding a semiconductor element over a water-washing tank while an upper sprayer and lower sprayers dispense water on either side of the element. After spraying, nitrogen gas through an upper nozzle drys one surface of the element. The element is then spun dry by being held upon platform by a vacuum chuck and rotated around an axis perpendicular to the platform.
Japanese PUPA No. 61-202334 published Sep. 8, 1986 for "Plate Work Treatment Unit" discloses a pan type dipping tank for immersing a plate in a liquid while the plate rotates around an axis perpendicular to plate. Valves in the tank are provided for adding and removing fluid. A suction head holds the plate in place by vacuum suction. Additionally, a sprayer may be positioned above the tank for dispensing liquid onto the plate during processing.
U.S. Pat. No. 4,677,759 issued Jul. 7, 1987 to Aigo for "Spin Drier for Semiconductor Material" discloses a drier apparatus having a table with semiconductor material arranged upon chucks located upon the periphery of the table surface. The table is rotated around a axis perpendicular to the table by a vertical shaft connected to a motor. Each material is held in position by a chuck having a spring and weight, such that the centrifugal force of the spin turns the material 90 degrees to position a ledge covering the material's edge.
U.S. Pat. No. 4,895,117 issued Jan. 23, 1990 to Niblet et al. for "Circuit Board Cleaning Apparatus" discloses the immersion in liquid of a carousel holding two circuit board, which are positioned at an angle to the lower plane of the tank. Cleaning is provided by agitating the boards in a solvent using reciprocal rotating motion of the carousel via a motor connected by a shaft at the center of the carousel.
U.S. Pat. No. 5,030,293 issued Jul. 9, 1991 to Rich et al. for "Method and Apparatus for Circuit Board Cleaning" discloses cleaning a circuit board by immersing a circuit board in liquid, and spraying liquids onto the circuit board in a chamber. The immersing or spraying is performed with either vertical oscillation of the board, or rotation about an axis perpendicular to the circuit board. Both motions are provided by an upper mechanism attached to a motor at one end, and at the other end, to arms extending to the edges of the circuit board. Sprayers are located circumferencily along the side walls of the chamber for directing fluids onto the board's upper portion, while a sprayer is located at the chamber bottom to direct fluids upon the board's lower portion. A valve assembly adds and drains liquids from the chamber. The board is dried by a hot, dry gas passed through the same sprayers. A board is loaded and removed from the chamber by a conveyer, and is automatically aligned in the chamber by the arms of the upper assembly.
IBM Technical Disclosure Bulletin, Vol. 19, No. 9, February 1977, pp. 3396--3396, shows a flux removal tool having substrates held in a flat carriage. The carriage is attached to a pivot connected to an upper rotary drive, and angled to the rotational axis of the rotary drive at the pivot. During the rotation of the carriage within a flow of an immersion liquid, the angle may be varied to provide optimum pressure of the liquid onto the substrate surface.
The advertising brochure MICROCEL Centrifugal Cleaning System from ACCEL Corp. dated 1989, advertises a programmable cleaning system for cleaning printed circuit boards in which the circuit board spins above the center of gravity to provide washing, rinsing and drying under tightly spaced components.